OF VITAL MOTION. 79 



mammals during a state of hybernation continues 

 almost to the same length of time as in reptiles. 



In sloths and lemurs, also, where the contractions 

 of the limbs continue a long time with little fatigue, 

 it would appear that this faculty is to be partially 

 ascribed to a peculiar division of the principal arteries 

 into a number of very small branches, by which means 

 the current of blood is broken, and the supply ren- 

 dered more defective than it would be if the main 

 channel remained pervious. 



A somewhat analogous fact to the one last cited is 

 to be found in cases of aneurism after the chief supply 

 of blood has been cut off by the ligature of the 

 vessel ; for there is a strong tendency to cramp of the 

 limb until the collateral circulation is established. 



The nature of the relation which exists between 

 the circulation and muscular action, however, is 

 exhibited with greater clearness in heemorrhage than 

 in any other case; and here it would appear that 

 spasm is the direct consequence of loss of blood, the 

 one being proportionate to the other : thus, when an 

 animal is bled to death by the butcher, it first passes 

 into a state of extreme jactitation very like chorea, 

 and then into epileptiform convulsions, which become 

 more and more decided as death draws nearer. Now 

 in this case it cannot be supposed that the convulsions 

 are dependent upon the operation of a stimulus, for 

 the generation of all organic force, whether nervous 



